Separation by centrifugal phenomena is based on the transfer of materials from one phase to another by mechanical means utilizing differences in particle density and size in mixtures under an applied centrifugal force field, Centrifugal separators have been used in industrial processes for at least one hundred years, as exemplified by early cream separators. Centrifuges are currently utilized in a broad spectrum of industry, including blood plasma separations, rubber latex concentration, penicillin solvent separation, wine clarification, municipal and industrial waste-water treatment for dewatering sludge, uranium mining, etc. Previously, centrifuges were conventionally classified as either a "settling" centrifuge (wherein particulates are removed by sedimentation) or "filter" centrifuge (wherein a liquid is forced through a filter medium by centrifugal action).
However, a new type of "centrifugal contactor" was developed by the Dept. of Energy in order to extract transuranic (TRU) elements from radioactive waste streams at nuclear processing plants. This device rapidly mixes the water-based nuclear waste in a first stream with a second stream containing an organic solvent that extracts the transuranic wastes. The two streams are individually introduced into a centrifugal contactor and thoroughly mixed such that the organic solvent may extract the TRUs with the centrifugal force applied to the mixture producing a clean separation of the solvent containing the TRUs from the waste water. By repeatedly mixing and separating the two phases, the centrifugal contactor can achieve relatively high levels of nuclear waste purification.
Heretofore, centrifugal contact separators have been used only in an environment exemplified by the nuclear waste separator described above, wherein two disparate fluids are mixed ("contacted") in an annular mixing zone so that an interaction between the two fluids can occur (such as the solvent extraction of transuranic waste from an aqueous waste stream). Such processes require that two separate and distinct fluids be handled, stored, transported and mixed. Such processes, and the apparatus to effect the process, ignore, the potential separation of disparate components already mixed with one another in a fluid system. For example, the separation of oil and water in a ship's bilges, the separation of solvents, fuels or other organic fluids spilled into lakes, streams, rivers or oceans, and any other application where rapid and efficient two-phase separation is desired in a fluid stream, do not necessarily require the addition of a second fluid to effect the separation of the two phases. Selective solvent extraction of a particular heavy metal is well known in, for example, pulsed extraction columns. However, such apparatus' are bulky and are not considered portable.
Therefore, there is a need for a centrifugal separator which can be used in a process wherein a single fluid having disparate components intermixed therein is introduced for separation of the various components, without the need to introduce a second fluid to be intermixed with the first fluid.